Field of the Invention
The present invention relates to wireless communications, and more particularly, to a method and apparatus for transmitting mobility-related information in a wireless communication system.
Related Art
Universal mobile telecommunications system (UMTS) is a 3rd generation (3G) asynchronous mobile communication system operating in wideband code division multiple access (WCDMA) based on European systems, global system for mobile communications (GSM) and general packet radio services (GPRS). A long-term evolution (LTE) of UMTS is under discussion by the 3rd generation partnership project (3GPP) that standardized UMTS.
A radio resource state (RRC) state indicates whether an RRC of a user equipment (UE) is logically connected to an RRC of a network. When an RRC connection is established between an RRC layer of the UE and an RRC layer of the network, the UE is in an RRC connected state (RRC_CONNECTED), and otherwise the UE is in an RRC idle state (RRC_IDLE). Since the UE in the RRC_CONNECTED has the RRC connection established with the network, the network can recognize the existence of the UE in the RRC_CONNECTED and can effectively control the UE. Meanwhile, the UE in the RRC_IDLE cannot be recognized by the network, and a core network (CN) manages the UE in unit of a tracking area (TA) which is a larger area than a cell. That is, only the existence of the UE in the RRC_IDLE is recognized in unit of a large area, and the UE must transition to the RRC_CONNECTED to receive a typical mobile communication service such as voice or data communication.
When the user initially powers on the UE, the UE first searches for a proper cell and then remains in the RRC_IDLE in the cell. When there is a need to establish an RRC connection, the UE which remains in the RRC_IDLE may establish the RRC connection with the RRC of the network through an RRC connection procedure and then may transition to the RRC_CONNECTED. The UE which remains in the RRC_IDLE may need to establish the RRC connection with the network when uplink data transmission is necessary due to a user's call attempt or the like or when there is a need to transmit a response message upon receiving a paging message from the network.
Enhancements for diverse data applications (eDDA) may be introduced in 3GPP LTE. Goal of the eDDA is reducing control signaling overhead in protocol layers. The eDDA can improve both control signaling and power efficiency for UEs based on traffic pattern, and obtain low cost from network or core network point of view. Low cost is typically the target for machine-type communication traffic, background traffic, offline traffic of interactive application, etc.
A method for transmitting mobility-related information efficiently, when a UE transits from RRC_IDLE to RRC_CONNECTED, may be required.